1. Field of the Invention
The present invention relates to an apparatus for measuring an anterior ocular segment capable of quantifying, for example, a protein concentration in the aqueous humor of an eye to be examined by measuring optical properties of the anterior segment of an eyeball of a person to be examined. More particularly, the present invention relates to an apparatus for measuring an anterior ocular segment in which improvement has been made regarding the positional adjustment (alignment) between the eye to be examined and the measuring apparatus, the display of an anterior ocular segment, and the storage of measurement data.
2. Description of the Related Art
A protein concentration (flare) and a cell number density in an anterior ocular segment reflect a disease of various symptoms including a postoperative inflammation. To quantitatively measure the protein concentration and the cell number density is clinically important. As a method of quantitatively measuring the protein concentration and the cell number density, there has been known a method in which an anterior ocular segment of a person to be examined is irradiated with a laser beam from a laser beam source, scattered light of the laser beam in the anterior ocular segment is received by a light receiving unit and converted into an electrical signal, and optical properties of the anterior ocular segment are calculated from the electrical signal.
As a measuring apparatus used for such a measuring method, an ophthalmologic measurement apparatus is disclosed in JP 64-017623 A. The ophthalmologic measurement apparatus is provided with a light receiving unit for monitoring. A virtual image on the surface of a cornea, of scattered light of a laser beam irradiated to the eye to be examined and the scattered light of the laser beam are received by the light receiving unit for monitoring. The positional adjustment (alignment) of the laser beam source and the light receiving unit for monitoring is performed in accordance with a position of the virtual image and a position of the scattered light on the light receiving unit for monitoring.
As the measuring apparatus, an ophthalmologic measurement apparatus is disclosed in JP 02-082938 A. The ophthalmologic measurement apparatus includes: an anterior ocular segment observing optical system having an objective for observing the anterior ocular segment of the eye to be examined; and an alignment optical system for projecting an index light for alignment to the eye to be examined commonly using the objective.
As the measuring apparatus, an ophthalmologic measurement apparatus is disclosed in JP 02-200236 A. In the ophthalmologic measurement apparatus, indexes for fixing a line of sight of the eye to be examined are located symmetric about the optical axis of the eyeball such that a positional relationship between the optical axis of the eyeball of the eye to be examined and the optical axis of the laser beam irradiation optical system at the irradiation of the laser beam in the case of the left eye to be examined becomes the same as the positional relationship therebetween in the case of the right eye to be examined.
As the measuring apparatus, an ophthalmologic measurement apparatus is disclosed in JP 03-264044 A. In the ophthalmologic measurement apparatus, the eye to be examined is irradiated with, for example, the above-mentioned laser beam. A signal which is received by the light receiving unit is processed to exhibit an alignment state to a measuring person. While an alignment index is displayed on the exhibited alignment state, whether or not the alignment is appropriate is exhibited by changing a color or a blinking rate of the alignment index.
With respect to a technique related to the measuring apparatus, an image processing system is disclosed in JP 2002-017681 A. In the image processing system, the same identification information is provided to an ophthalmologic image which is photographed by, for example, an ophthalmologic image taking apparatus and image-taking conditional information which is inputted by an input device. The ophthalmologic image and the image-taking conditional information are transferred as information for taking image to the ophthalmologic image taking apparatus.
With respect to a technique related to the measuring apparatus, a system for taking an image of an eye to be examined is disclosed in JP 2001-275979 A. In the system for taking an image of an eye to be examined, an image of the eye to be examined, which was photographed, for example, in the past and in which a region is set in advance on the image, is recorded. In current photographing, a photographing condition of the eye to be examined is set based on information of the region on the recorded image.
In the above-mentioned measuring method, the positional adjustment (alignment) between the laser beam source and the light receiving unit and the eye to be examined is important in accurately measuring the anterior ocular segment. However, the measuring apparatuses have some problems in accurately measuring the anterior ocular segment.
One example of the ophthalmologic measurement apparatuses is an apparatus that performs the alignment while viewing the anterior ocular segment of the eye to be examined from an oblique direction through an eyepiece. With such an apparatus, it is hard to perform alignment because the measuring person does not face the person to be examined. In addition, because the observation is performed using the eyepiece in the apparatus, it causes inconvenience for the measuring person when performing the alignment. Further, because, the measurement results are likely to reflect a skill in operation of the measuring person, and therefore, it is hard to perform the anterior ocular segment measurement having high reproducibility.
Another example of the ophthalmologic measurement apparatuses is an apparatus in which the alignment index is not exhibited. In such an apparatus, even if the alignment is attempted using as a guide the virtual image resulting from the scattered light, reflected light, or the like on the anterior ocular segment, a suitable position is not exhibited, so that the alignment largely depends on the judgment of the measuring person. Therefore, it is hard to perform the anterior ocular segment measurement having high reproducibility using the apparatus.
When the techniques related to the ophthalmologic measuring apparatus are applied to the above-mentioned ophthalmologic measuring apparatuses, they are advantages in that previous measurement conditions and previous measurement results with respect to the same measuring person and previous measurement conditions and previous measurement results with respect to another measuring person can be utilized for further measurement and diagnosis. However, in some cases, alignment operations performed on each image and indexes used are different from one measuring person to another or even different for the same measuring person at different times. Therefore, even when the alignment is performed using such techniques, it is hard to perform the anterior ocular segment measurement having high reproducibility in some case.
In the above-mentioned ophthalmologic measuring apparatuses, when the measurement position is shifted, the intensity of reflected light and the intensity of scattered light on the anterior ocular segment change, and affect a background value and a signal value. Therefore, even when the same eye is measured plural times by the same measuring person at the same day, a variation in measurement results is caused in some cases. Thus, in order to accurately judge a change with the passage of time of the eye to be examined, it is desirable that the alignment having high reproducibility is accurately performed for the anterior ocular segment measurement.